I've seen screenshots of their Tweets, which were identical, so presumably were coordinated. The originator of the video (whose Twitter account has now been deleted) has a history of extreme right-wing posts.
Considering the number of Tweets which were recycled of supposedly anti-Semitic posts and other stuff, those three need to be held to account.
I always did think they were fairly awful human beings, but they've gone down even further in my estimation. Lucy Allen was involved in some dodgy stuff a couple of years ago, including alleged bullying of her PA and lying about death threats - it was all hushed up.
I don't think Starmer will sue, but he's mature, intelligent and knowledgeable of the law enough to deal with it.